Answer: Many of the men had been high-ranking officers in the Confederate armies or men of position in the Confederate government.
Step-by-step explanation:
When Congress resumed after the Civil War, many southern states simply sent representatives who were high ranking officers in the Confederate armies to congress. For instance, the Confederate Vice President, Alexander Stephens were elected to Senate and eventually became Governor of Georgia.
These acts enraged many in the North as they saw the South as unrepentant. Indeed, these new members of congress even opposed more rights for black people in congress further compounding the northern outrage.